; CC65 runtime: division for unsigned ints
;
- .export tosudiva0, tosudivax, udiv16
- .import popsreg
- .importzp sreg, ptr1, ptr4
+ .export tosudiva0, tosudivax, udiv16
+ .import popsreg
+ .importzp sreg, ptr1, ptr4
tosudiva0:
ldx #$00 ; Clear high byte
tosudivax:
- sta ptr4
- stx ptr4+1 ; Save right operand
- jsr popsreg ; Get left operand
+ sta ptr4
+ stx ptr4+1 ; Save right operand
+ jsr popsreg ; Get left operand
; Do the division
- jsr udiv16
+ jsr udiv16
; Result is in sreg, remainder in ptr1
- lda sreg
- ldx sreg+1
- rts
+ lda sreg
+ ldx sreg+1
+ rts
;---------------------------------------------------------------------------
; 16by16 division. Divide sreg by ptr4. Result is in sreg, remainder in ptr1
; (see mult-div.s from "The Fridge").
; This is also the entry point for the signed division
-udiv16: lda #0
- sta ptr1+1
- ldy #16
+udiv16: lda #0
+ sta ptr1+1
+ ldy #16
ldx ptr4+1
beq udiv16by8a
-L0: asl sreg
- rol sreg+1
- rol a
- rol ptr1+1
+L0: asl sreg
+ rol sreg+1
+ rol a
+ rol ptr1+1
- pha
- cmp ptr4
- lda ptr1+1
- sbc ptr4+1
- bcc L1
+ pha
+ cmp ptr4
+ lda ptr1+1
+ sbc ptr4+1
+ bcc L1
- sta ptr1+1
- pla
- sbc ptr4
- pha
- inc sreg
+ sta ptr1+1
+ pla
+ sbc ptr4
+ pha
+ inc sreg
-L1: pla
- dey
- bne L0
- sta ptr1
- rts
+L1: pla
+ dey
+ bne L0
+ sta ptr1
+ rts
;---------------------------------------------------------------------------
; 16by8 division
udiv16by8a:
-@L0: asl sreg
- rol sreg+1
- rol a
+@L0: asl sreg
+ rol sreg+1
+ rol a
bcs @L1
- cmp ptr4
- bcc @L2
-@L1: sbc ptr4
- inc sreg
+ cmp ptr4
+ bcc @L2
+@L1: sbc ptr4
+ inc sreg
-@L2: dey
- bne @L0
- sta ptr1
- rts
+@L2: dey
+ bne @L0
+ sta ptr1
+ rts